Method of production of 4,4-dimethyl-1,3-dioxane

ABSTRACT

1. IN THE PROCESS FOR THE PRODUCTION O 4,4-DIMETHYL1,3-DIOXANE BY REACTING ISOBUTYLENE WITH FORMALDEHYDE IN A LIQUID-LIQUID SYSTEM IN THE PRESENCE OF AN ACIDIC CATALYST SELECTED FROM THE GROUP CONSISTING OF SULFURIC ACID, PHOSPHORIC ACID AND SULFONIC ACID, THE IMPROVEMENT WHICH COMPRISES EMPLOYING ISOBUTYLENE IN AN AMOUNT OF MORE THAN 0.5 MOLE PER MOLE OF FORMALDEHYDE AND CARRYING OUT THE REACTION WHILE MAINTAINING THE CONVERSION OF FORMALDEHYDE NOT EXCEEDING 85 PERCENT BY CONTROLLING THE REACTION CONDITIONS AND STIRRING THE REACTION SYSTEM UNDER AN AGITATION POWER OF BETWEEN 0.4 AND 2 HORSEPOWER PER CUBIC METER, SAID AGITATION POWER BEING A VALUE CALCULATED ACCORDING TO THE FOLLOWING EQUATION:   P=NP.P.(N/60).L/GE X 75   WHEREIN P IS THE AGITATION POWER (HORSEPOWER), NP IS THE POWER NUMBER (A CONSTANT DIFFERING IN ACCORDANCE WITH THE CLASS OF VANES AND OBTAINED FROM THE RUSHTON DIAGRAM), P IS THE DENSITY OF REACTION LIQUID (KG./M.3), N IS THE REVOLUTIONS PER MINUTE (R.P.M.), L IS THE DIAMETER OF THE TURBINE (METER), AND GE IS THE GRAVITATIONAL CONVERSION FACTOR (KG-M./KG.SEC.2).

I Get. 1, 1974 KOICHI KU-SHIDA E'I'AL 3,839,362

METHOD OF PRODUCTION OF 4,4-DIMETHYLflJ-DIOXANE Filed Dec. 27. 1971United States Pate t 3,839,362 METHOD OF PRODUCTION OF 4,4-DIMETHYL-1,3-DIOXANE Koichi Kushida, Fumio Nakahara, Toshio Kawaguchi, and KaichiSuzuki, Kurashiki, Japan, assignors to Kurray Co., Ltd., Kurashiki,Japan Filed Dec. 27, 1971, Ser. No. 212,141 Claims priority, applicationJapan, Dec. 28, 1970, 46/130,001 Int. Cl. C07d 15/04 US. Cl. 260-340.7 6Claims ABSTRACT OF THE DISCLOSURE In the process for the production of4,4-dimethyl-1,3- dioxane by reacting isobutylene with formaldehyde inthe presence of an acidic catalyst, the improvement which comprisesemploying isobutylene in an amount of more than 0.5 mole per mole offormaldehyde and carrying out the reaction while stirring the reactionsystem under an agitation power of at least 0.4 horsepower per cubicmeter and controlling the reaction in such a manner that the conversionof formaldehyde does not exceed 85 percent.

This invention relates to an improved method of producing4,4-dimethyl-l,3-dioxane by reacting isobutylene and formaldehyde in thepresence of an acidic catalyst.

That 4,4-dimethyl-1,3-dioxane (hereinafter referred to as MDO), anintermediate for the synthesis of isoprene, can be produced by reactingisobutylene with formaldehyde in the presence of an acidic catalyst iswell known as a typical example of the Prins reaction. In practice thisreaction is usually carried out in a liquid-liquid system by mixing amixture of C hydrocarbons containing isobutylene (usually referred to asBB fraction or C fraction) with an acidic catalyst, such as sulfuricacid, and an aqueous formaldehyde solution, followed by heating themixture under pressure. In the past isobutylene and formaldehyde wereusually used in such a proportion that the mole ratio of isobutylene toformaldehyde was not greater than 0.5.

However, this conventional method has the shortcoming that due to thefact that formaldehyde is present in excess relative to isobutylene andthat the extraction with isobutylene of the resulting MDO is poor, sidereactions such as shown in the following equation (1) below arepromoted, with the consequence that the selectivity for MDO (the termselectivity, is used, to define the proportion of formaldehyde orisobutylene that is converted to MDO, calculated based on the reactedformaldehyde or isobutylene) declines. Moreover, the by-productsobtained from this MDO and formaldehyde are not easily decomposed toeither MDO or isobutylene and formaldehyde. Therefore, it is verydesirable that the side reactions shown in equation (1) are inhibitedduring the reaction for synthesizing MDO.

Gigi /CH -CIQ (1) 0E3 CI-h-CH; /CI3 C O CHzO CHzCHg OCH I CH3 OCH1 0HFormaldehyde MBO CHaOH CH: HCHz An object of the present invention is toprovide a new and improved method of producing MDO, which does notpossess the above described shortcoming.

Another object of this invention is to provide an ef fective method ofagitating a reaction system consisting of isobutylene, formaldehyde andan acidic catalyst.

Further objects and advantages will be apparent from the followingdescription and the appended claims.

FIG. 1 is a schematic view illustrating a standard flatblade turbine,which is conveniently used for carrying out the agitation of thereaction system in practicing the method of the invention.

In accordance with the present invention an improved method of producingMDO is provided by reacting isobutylene with formaldehyde in thepresence of an acidic catalyst in which isobutylene is employed in anamount of more than 0.5 mole per mole of the formaldehyde, and thereaction is carried out while stirring under an agitation power of atleast 0.4 horsepower per cubic meter and the reaction is controlled insuch a manner that the conversion of formaldehyde does not exceedpercent.

As a consequence of this improved process of the invention, not only canthe side reactions shown in the foregoing equation (1) be inhibited butalso the production of MDO at a high selectivity is made possible.Therefore, this process is commercially of great advantage.

These excellent results of the invention are believed to be due to thefollowing reason: that is, when isobutylene or a C fraction is used inexcess of formaldehyde, isobutylene or other C; hydrocarbons whichremain unreacted act as an extraction agent for MDO that is continuouslyproduced as the reaction proceeds, to reduce the possibility of thecontact between MDO and formaldehyde. In addition, the effective contactthat is brought about between isobutylene and formaldehyde as a resultof the vigorous agitation is believed to act synergistically with theforegoing extractive action to bring about the excellent resultsdescribed hereinbefore.

It is important in this invention that isobutylene and formaledhyde usedas the starting materials are fed to the reaction system in a specificmolar relationship. It is of critical importance that the mole ratio ofisobutylene to formaldehyde (isobutylene/formaldehyde) is more than 0.5/1, and preferably more than 0.65/1. No particular upper limit isimpassed as to the mole ratio. However, the feeding to the reactionsystem of an unnecessarily great amount of isobutylene or a C fractioncontaining isobutylene should be avoided, since it is uneconomical insuch respects as equipment and heat required as well as the recoveryoperation. Therefore, it is best to hold the aforesaid mole ratio to atmost 1:1.

The term agitation power, as used herein and the appended claims, meansthe energy per unit time and per unit volume that is imparted to theliquid mixture to be agitated inside the reaction system. This energycan usually be imparted by any of the various agitating apparatus thatare used in the agitation of a liquid-liquid mixture, such as the paddletype agitator, propeller type agitator, turbine type agitator, orificemixer, venturi mixer, nozzle mixer, jet agitator, and the like. Thepreferred agitating apparatus from the standpoint of agitationefficiency is an agitator having agitating vanes, and especially anagitator having the standard fiat-blade turbine, such as that shown inthe accompanying drawing FIG. 1.

For imparting a desirable agitation effect to the reaction mixture in anagitation such as described, the agitation power should be at least 0.4horsepower per cubic meter, preferably at least 0.6 horsepower per cubicmeter, of the reaction mixture in the reactor, and still more preferablyin the range between 0.6 and 2 horsepower per cubic meter of thereaction mixture in the reactor.

This agitation power is usually calculated as follows:

wherein:

P is the agitation power (horsepower: HP),

Np is the power number (a constant differing in accordance with theclass of vanes and obtained from the Rushton diagram),

p is the density of reaction liquid (kg./m.

N is the revolution per minute (r.p.m.),

L is the diameter of the turbine (meter), and

Ge is the gravitational conversion factor (kg.-m./

kg.-sec.

The Rushton diagram is obtained by plotting the relation between theReynolds Number and the Power Number (Np) of an industrial agitator on asemi-log scale as disclosed initially by J. H. Rushton, et al., inChemical Engineering Progress, Vol. 46, No. 8, pp. 395-404 (1950) andVol. 46, No. 9, pp. 467-476 (1950). The Rushton diagram shown at Vol.46, No. 9, page 470 is the one used in this invention.

When the agitator having the standard flat-blade turbine, such as shownin FIG. 1, is used, the agitation power is frequently substituted by thepumping capacity of the impeller. For example, the pumping capacity ofthe impeller 9 of the standard flat-blade turbine illustrated in FIG. 1(L:l:b=1/2:l/5) can be calculated as follows:

9: b (1rL/ 2) N wherein 9 is the pumping capacity of the impeller(mfi/minute), b is width of the vanes (meter),

L is the diameter of the turbine (meter), and

N is the revolutions per minute (r.p.m.) of the turbine.

Since the quantitative relationship between the pumping capacity of theimpeller and the agitation power varies widely in accordance with thechange in N and L in this case, an unqualified statement cannot be maderegarding this relationship, but from the results obtained in the caseof the reactor and agitator used in the hereinafter given examples it isrecommended that the stirring be so carried out that the pumpingcapacity of the impeller resulting from the agitation becomes at least 5cubic meters per minute, and preferably at least 7 cubic meters perminute, per cubic meter of the reaction mixture in the reactor in thecase where a standard flat-blade turbine is used.

While MDO can be obtained at a high selectivity from isobutylene andformaldehyde according to the hereinbefore described novel and improvedprocess of the instant invention, it was also found that especially goodsynergistic aifects could be obtained when the reaction was socontrolled that the conversion of formaldehyde does not exceed 85percent, and preferably not exceed 80 percent. For example, in the casewhere the mole ratio of isobutylene to formaldehyde is 0.6-0.8 and theagitation power 0.7- 0.9 horsepower per cubic meter, a maximumselectivity for MDO based on the converted formaldehyde (above 95-percent) can be obtained when isobutylene and formaldehyde are reactedin the presence of a sulfuric acid catalyst up to a certain point in therange of 76-85 percent conversion of formaldehyde. On the other hand,when the conversion of formaldehyde reaches above the foregoing range(i.e. above 85 percent), side reactions such as shown in thehereinbefore given equation (1) are promoted and the formed MDO isconsumed resulting in a considerable drop in selectivity for MDO. Forinstance, the MDO' selectivity declines to about 90 percent at aconversion of formaldehyde of 88 percent. Therefore, this results in acommercial disadvantage.

The restriction from the theoretical standpoint is imposed with respectto the lower limit of the conversion of formaldehyde. From theviewpoints of the cost of production and the ease of operations, theconversion of formaldehyde is preferably at least 50 percent.

The method of the invention is performed by introducing isobutylene,formaldehyde and an acidic catalyst in a specific quantitativerelationship to a reaction vessel equipped with a desirable stirrer,such as an agitator having a standard flat-balde turbine and conductingthe re action with stirring under a pressure under which the reactionsystem can be maintained in the liquid phase at a reaction temperatureof about 50-80 C. The process may be carried out either by a batchwisemethod or in a continuous manner.

While isobutylene having a high purity can be used as the startingmaterial, it is particularly preferred to use a C fraction whoseisobutylene content is in the range of about 15-50 percent by weight inview of the greatness of the C fractions extraction effect on MDO. Onthe other hand, formaldehyde is generally used in the form of an aqueoussolution of a concentration of 30-60 percent by weight. The acidiccatalysts which can be used in the method of the invention includesulfuric acid, phosphoric acid and sulfonic acid, and the like. The mostconvenient acidic catalyst is sulfuric acid. The amount of formaldehydeto be fed can be such that the mole ratio of formaldehyde to catalyst(formaldehyde: catalyst) is in the range between 1:0.1 and 1:0.3.

The reaction mixture, which has been obtained by the hereinabovedescribed method, is then separated into an organic layer and an aqueouslayer either by decantation or other conventional techniques. This isfollowed by recovering MDO from the organic layer by, for example,distillation, while the catalyst can be recovered from the aqueous layerand recycled for reuse.

The so obtained MDO can be advantageously used for producing isoprene bycatalytically decomposing the same.

The following examples are given for specifically illustrating theinvention. However, the invention is not intended to be limited to theseexamples.

EXAMPLE I A 10-liter vigorous agitation type reactor having an insidediameter of millimeters and equipped with two standard flat-bladeturbines (diameter of turbine: 50 millimeters) was continuously fed with11 liters per hour of an aqueous formaldehyde solution (formaldehydecontent: 50% by weight) '5 liters per hour of an aqueous sulfuric acidsolution (sulfuric acid content: 30% by weight) and a 0.; fraction(isobutylene content: 45% by weight) at a flow rate indicated in Table1, below; and the reaction was carried out at a temperature of 65 C. andunder a pressure of 10 kg./cm. gauge while stirring the liquid mixturein such an extent that the pumping capacity of the impeller was 7.5cubic meters per minute per cubic meter of capacity of the reactor(agitation power of 0.52 horsepower per cubic meter). The resultsobtained are shown in Table 1.

TABLE 1 Percent MDO selec- Flow rate of C4 Isobutylene/ tivity based onfraction formaldehyde Conversion of reacted (liter/hr.) (mole ratio)formaldehyde formaldehyde Run Nos. 1 and 2 of the foregoing table arecontrols in which the molar ratio of isobutylene to formaldehyde isoutside the scope of the present invention. It can be seen that the MDOselectivity based on the reacted formaldehyde in the case of Run Nos. 1and 2 is greatly inferior to those of Run Nos. 4 and 5, which areembodiments of the instant invention.

5 EXAMPLE n Into a 10-liter vigorous agitation type reactor having aninside diameter of 150 millimeters and equipped with two standard flatblade turbines (turbine diameter: 50

Run Nos. 1 and 2 in the foregoing table are controls in which theagitation power is outside the scope of this invention. It can be seenthat in the case of these controls the conversion (rate of reaction) offormaldehyde and the selectivity for the formation of MDO are greatlymillimeters) an aqueous formaldehyde solution (form- 5 aldehyde content:30% by weight), a concentrated sul- Inferior? 2 3 F3 ii are mconformfuric acid (sulfuric acid conent: 97% by weight) and anlce W t 6me 0 o e q 1 a C fraction having an isobutyl content indicated in ByWaypf companson pulsating extfactlon umn Table 2, below, were fed flowrates of 18, 2 and 32.5 y reacpon 'aPParams not equlppqd f an t i litersper hour, respectively; and the reaction was carried (Inside dlarpeter'mete; and f g out at a temperature of 65 C. under a pressure of 10equlppfa'd i Perforated p ates haYmg 9 es 0 m1 1- kg./cm. gauge whilestirring .the foregoing mixture to meter i qmmeter an opemng i of E Suchan extent that the pumping capacity of the impeller a pulsating device)was used; and the reaction was carried was 8.75 cubic meters per minuteper cubic meter of out l charging to reacnon apparatu? an aqueous thecapacity of the reactor (ag tation Power of 0.83 sol'unon fconcentration of 30%.by Welghf at a flow horsepower per cubic meter).The results obtained are rate of 18 mars per l fractlon of anlsoputylene Shown in Table 2 below content of 45 by weight at a flowrate of 32 liters per hour and sulfuric acid at a flow rate of 2 htersper hour TABLE 2 and countercurrently contacting the C fraction with thePercent 20 aqueous formaldehyde solution and sulfuric acid, while 583MDO 581% employing the pulsating conditions of pulsatory frequency 0.fraction Isobutylene/ tivity based of 140 cycles per minute and apulsatory amplitude of P 5 s fif zg f li ag ggggiffggggg 353333? 10millimeters. In this case the residence time of the reaction liquid inthe reactor was about 4.7 times that g3 8 2? 83:8 of the case describedin Example 'I'II, above. Notwith- 31 0.55 72 93.2 standing thisincreased residence time, the results of the 2% 8 Z; gg g reaction weresuch that the conversion of formaldehyde 45 0.80 80 96.4 was 78% and theselectivity for the formation of MDO th b1 1 h h based on the reactedformaldehyde was 85% Run No. 1 in e foregoing ta e is a contro in w ic II the mole ratio of isobutylene to formaldehyde is outside EXAMPLE IVthe scope of the instant invention. It is seen that the An agitated tankreaction apparatus identical to that MDO selectivity based on thereacted formaldehyde in used in Example III was employed, and thereaction was this case is inferior to those of Run Nos. 26, which arecarried out continuously at a temperature of 60 C. and embodiments ofthe present invention. 35 under a pressure of 10 kg./cm. gauge, using anaqueous formaldehyde solution of a concentration of 50% by EXAMPLE Inweight, a 30% aqueous sulfuric acid solution and a C A 10-liter agitatedtank reaetiOIl apparatus of an fraction of an isobutylene content of byweight. The inside diameter of 150 millime rs and equippe W h agitatorwas operated at 700 r.p.m., and the agitation powtWO standard flatadturbines (turbine diameter 40 er per unit volume was 0.83 horsepower percubic meter. millimeters) was used, and the reaction was carried out Theconversion of formaldehyde was changed by varying at a temperature of C.and under a pressure of 10 the residence time. The results obtained areshown in kg./cm. gauge while introducing an aqueous formalde Table 4,below.

TABLE 4 Rate of-- Percent Aqueous MDO formaldehyde selectivity solution04 feed Sulfuric Isobutylene/ Conversion based on feed (liter/ acid feedformaldehyde of reacted liter/hr. hr.) (liter/hr. (mole ratio)formaldehyde formaldehyde 20. 0 62 8. 7 0. 76 61 92. 7 17. 0 53 7. 4 0.76 e7 93. 6 11.0 34 4.8 0.76 76 94.8 9.0 28 3.9 0.76 33 93.5 7. 2 22 a.1 0.76 as 89. 5 6. 0 19 2. 6 0. 76 91 87. 6

hyde solution of a concentration of 30% by weight, a concentratedsulfuric acid and a C fraction containing 45 by weight weight ofisobutylene into the foregoing reaction apparatus at flow rates of 18, 2and 32 liters per hour, respectively. Reaction results such as shown inTable 3, below, were obtained by varying the agitation power. In thisexperiment the average residence time inside the agitation tank of thereaction liquid was about 12 minutes.

Run Nos. 5 and 6 in the foregoing table are controls in which theconversion of formaldehyde is outside the scope of this invention. It isaparent that the selectivity for MDO formation based on the reactedformaldehyde is greatly inferior in the case of these controls ascompared with those of Run Nos. 1-4, which are in conformance with theinvention process.

What is claimed is:

65 1. In the process for the production of 4,4-dimethyl- TABLE 31,3-dioxane by reacting isobutylene with formaldehyde in percent aliquid-liquid system in the presence of an acidic catalyst Agitation MDO581% selected from the group cons sting of-sulfuric acid, phospowerPumping tivity ba eg phoric acid and sulfomc acid, the improvement whichge y glu iiig ori e il ei fifitf... comprises employing isobutylene inan amount of more (r-p-m-) dehyde hyde than 0.5 mole per mole offormaldehyde and carrying 400 77 out the reaction while maintaining theconversion of 450 0.22 5.6 35 32 550 0.4. 6.1 77 92 formaldehyde notexceeding 85 percent by controlling the $88 312% 5? 3g 8: reactionconditions and stirring the reaction system under 1,000 82 92 anagitation power of between 0.4 and 2 horsepower per cubic meter, saidagitation power being a value calculated according to the followingequation:

wherein P is the agitation power (horsepower);

N is the power number (a constant difiering in accordance with the classof vanes and obtained from the :Rushton diagram);

1 is the density of reaction liquid (kg/mi N is the revolutions perminute '(r.p.-m.);

L is the diameter of the turbine (meter); and

Ge is the gravitational conversion factor '(k-g.-m./kg.-

'sec.

2. The process of Claim 1 wherein isobutylene is employed in an amountof more than 0.65 mole per mole of formaldehyde.

3. The process of Claim 1 wherein isobutylene is em- 8 ployed in anamount of below 1 mole per mole of formaldehyde.

4. The process of Claim 1 wherein the reaction is carried out withstirring under an agitation power of at least 0.6 horsepower per cubicmeter.

5. The process of Claim '1 wherein the reaction is carried out withstirring under an agitation power of between 0.6 and 2.0 horsepower percubic meter.

6. The process of Claim 1 wherein the reaction is carried out whilemaintaining the conversion of formaldehyde at a rate of between 50 and80 percent by controlling the residence time in the reactor.

DONALD G. DAUS, Primary Examiner 20 J. H. TURNIPSEED, Assistant ExaminerUl i'li S'IWJAES EA'i'EN'l )FuETi-(HF) \g'w I") r'}'\' 1 l w I r {"1 fiA('\v1 1 rqT'f {f {AL i if 1 [J13 J31 LJ \1 L1 1.91. it 11 .5. .ik/JiPatent 3,839,362 I Dated October 1, 1974 a I O .T.nventor(s) KOlchlKUSHIDA, vET AL.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

At column 3, lines 2-4, and at column 7, lines 3-5, change the formulato read:

"' P Np -7 (N/60)3 L Ge X 75 sixteenth ,D a 0f March 9 76 [SEAL] Arrest.

RUTH C. MASON C. MARSHALL DANN Arresting Officer (ommisxinnvr oflarentsand Trademarks UNITED STATES PATENT OFFICE' "a (IERTIFICATE OFCORRECTION Patent No. 3,839 ,362 Dated October 1, 1974 Inventor(s) IKo-ichi KUSHIDA ET AL V i Y It is certified that error appears in theabove-identified patent I and that said Letters Patent are herebycorrected as shown'belowz Inthe Heading, correct the spelling of theAssigfie to read as follows:

-- Kuraray Co. Ltd.

Signed and sealed this 14th day of January 1975.

(SEAL) Attest:

McCOY M'. GIBSON JR. c; MARSHALL DANN Attesting Officer Commissioner ofPatents ORM Po-1o5o (10-69) USCOMM-DC eos'Ia-pes i 0.5. GOVZRNMENTHUNTING OFFICE I969 0-365-331.

1. IN THE PROCESS FOR THE PRODUCTION O 4,4-DIMETHYL1,3-DIOXANE BYREACTING ISOBUTYLENE WITH FORMALDEHYDE IN A LIQUID-LIQUID SYSTEM IN THEPRESENCE OF AN ACIDIC CATALYST SELECTED FROM THE GROUP CONSISTING OFSULFURIC ACID, PHOSPHORIC ACID AND SULFONIC ACID, THE IMPROVEMENT WHICHCOMPRISES EMPLOYING ISOBUTYLENE IN AN AMOUNT OF MORE THAN 0.5 MOLE PERMOLE OF FORMALDEHYDE AND CARRYING OUT THE REACTION WHILE MAINTAINING THECONVERSION OF FORMALDEHYDE NOT EXCEEDING 85 PERCENT BY CONTROLLING THEREACTION CONDITIONS AND STIRRING THE REACTION SYSTEM UNDER AN AGITATIONPOWER OF BETWEEN 0.4 AND 2 HORSEPOWER PER CUBIC METER, SAID AGITATIONPOWER BEING A VALUE CALCULATED ACCORDING TO THE FOLLOWING EQUATION: